Barrel clutch for reversible drives



Dec. 25, 1962 E. GALLAS 3,070,200

BARREL CLUTCH FOR REVERSIBLE DRIVES Filed Jan. 19. 1959 2 Sheets-Sheet 1 FIG! FIG. 2

ErnsT GALLAS a WM,M+PJ

INVENTOR:

Dec. 25, 1962 E. GALLAS 3,070,200

BARREL CLUTCH FOR REVERSIBLE DRIVES Filed .Jan. 19, 1959 2 Sheets-Sheet 2 IN VENTOR.

frns'i' GALLAS United States Patent i 3,d7tl,200 BARREL (ILUTQH FOR REVERSIBLE DRIVES Ernst Gallas, Hannover, Germany, assignor to Protona Produktionsgesellschaft fiir Elektroakustische Gerate G.rn.b.H., Hamburg, Germany Fiied Jan. 19, 1959, Ser. No. 787,705 Claims priority, application Germany Jan. 18, 1958 4 Claims. (Cl. 192-48) This invention relates to a barrel clutch for reversible drives, particularly of the kind employed in sound recording apparatus, though also suitable for employment in reversible drives of any other kind especially in connection with precision apparatus.

Barrel clutches for reversible drives in magnetic sound recording apparatus which provide an inertial flywheel mass elastically coupled with the driving wheel are already known. In such clutches the driving wheel is coupled either directly or by means of an elastic belt with the driving motor, such as an electric motor. In reverse operation the majority of sound recorders are run at a much higher speed than in forward operation. These different speeds are obtained by using barrel clutches with engaging faces of different pitch diameters. The engaging faces are mechanically connected optionally either with one or the other of the driving discs of the spool spindles. To this end the conventional type of barrel clutch is shifted axially in the direction of the connecting line between the spool spindles.

An electromagneti-cally operated shiftable friction clutch for magnetic sound recorders is also known in which a cup-form magnet is disposed concentrically underneath the spool.

For film drive mechanisms, eddy current brakes have been employed. However, these drives do not incorporate a clutch.

In magnetic sound recorders which employ a wire as the magnetic record carrier use has been made of a controllable magnetic clutch.

The present invention relates to a barrel clutch which is especially adapted to satisfy the various requirements of driving means for magnetic sound recording apparatus. The invention consists in that clutch engagement and disengagement is electrically controlled and that the braking effort is electromagnetically applied in accordance with the desired speed of the record carrier and assisted by frictional forces. Another feature of the invention consists in that the electromagnetic clutch means consist of an extraneously energised cup-form magnet which simultaneously provides a flywheel mass and of an armature in the form of a clutch disc provided with an entraining surface. According to the invention the magnetic brake consists of an extraneously energised fixed magnet which acts upon the clutch disc by embracing part of the periphery of the disc so as to leave an intervening air gap. The retarding power of the electric brake can be controlled by adjusting the energisation of its magnet. As as additional feature of the present invention, each of the optionally driven spindles is associated with a separate electric clutch and an electric brake, the entire assembly being combined in a single barrel.

The present invention enables the barrel clutch to be constructed with a minimum of parts. It can be manufactured at low cost since production tolerances are relatively wide. Moreover, unlike the form of construction in which barrel clutches are shiftable between the spool spindles, the barrel clutch of the present invention can be a fixture in the driving mechanism and operated solely by electrical means without the provision of shift members subject to wear or other movable components.

A preferred embodiment of the invention is shown by way of example in the accompanying drawings which illusice strate a barrel clutch with two clutch faces of different pitch diameters comprised in one barrel to provide different forward and reverse running speeds.

In the accompanying drawings FIG. 1 is a side elevation of the barrel clutch schematically showing its connection with an electric driving motor;

FIG. 2 is -a horizontal section of the barrel clutch taken on the line II--H of KG. 1; and

FIG. 3 illustrates an electric circuit for controlling the barrel clutch brakes.

As shown in FIG. 1, a baseplate 1 is provided with upright bearing brackets 2, 2a for the half shafts 3, 3a of a barrel clutch denoted as a unit by reference numeral 4. Each half shaft 3 and 3a of the running shaft of the barrel clutch 4 rotatably carries a collar 5 and 5a for the retention of the clutch discs 6 and 7 which have entraining faces 8 and 9 respectively of different pitch for the frictional engagement of the associated spindle tables which are not shown. The two half shafts 3 and 3a are in alignment and abut in axial contact with the intervention of a ball 10 consisting of a paramagnetic material. 7 A one-piece hollow sleeve 11 is pushed with a running fit over the two half shafts 3 and 3a. This sleeve carries two independent hollow cores i2, 13 of ferromagnetic material. The two inside reduced ends of the hollow magnetic cores are mechanically connected together by means of a non-magnetic bush 14. A pulley 15 can rotate on bush 14 under the control of a spiral spring 16 which connects pulley 15 and bush l4. Pulley 15 may be in the form of a wheel having a grooved rim, and may be driven from a pulley 13 of a motor 19 by means of an elastic belt 17.

Secured to the hollow cores 12, 13 on each side of pulley 15 are magnet casings 20, 21 which together with the hollow cores 12, 13 and inserted coil windings 22, 23 form cup-form magnets with hollow cores of a well known type. The windings of both magnets are energised by a source of electrical power and are supplied with current through sliprings 24-, 25 mounted on an intermediate insulation 26, 26a.

The cup-form magnets and their windings constitute the flywheel mass of the barrel clutch, and are elastically coupled through a spiral spring 15 with the driving pulley 15.

Part of the air gap of each cup-form magnet is reduced by a ferro-magnetic ring 27, 27a respectively mounted on the hollow magnet cores 12 and 13. Opposite the remaining adjacent air gap is a copper short-circuiting ring 28, 28a fitted into each clutch disc 6 and 7.

Part of the periphery of each clutch disc 6, 7 is embraced by a fixed magnet 29 and 3t} having pole-pieces partially embracing the clutch discs, leaving a small intervening air gap. These magnets 29, 30 are braking magnets and comprises energisable windings 29a: and 300. As shown in FIG. 3 the braking magnets 29, 30 obtain their energising current from a source of power ST of which the minus pole is earthed whilst the positive pole optionally energises one of the magnets according to the position of a brake switch 31. The brake switch 31 is operated by the control knobs and push buttons of the magnetic sound recorder and makes connection either with contact 31a or 31b, thus causing either the braking magnet 29 or 30 to be energised. The retarding effect of braking magnet 39 can be controlled by adjustment of otentiometers 30 h or 2%.

The barrel clutch as here-in described is operated and controlled as follows:

Assuming motor 19 is running barrel clutch 4- is rotated and that it is now desired that clutch disc 7 entrain the associated spindle disc, then winding 23 is energised through slip ring 25. The associated cup-form magnet will then cause clutch disc 7 to be engaged and the corresponding spindle disc, which is not shown on the drawings, will be entrained. Winding 22 will not be energised so that the other spindle disc and its associated clutch disc 6 will idle freely. For reversing the drive, winding 22 is energised so that the relative cup-form magnet will now engage clutch disc 6, Whereas clutch disc 7 and its spindle plate are released and can freely idle. A special running brake for the idling clutch disc is not required in a barrel clutch according to the present invention. The necessary braking effort is provided by the friction of the clutch disc 6 or 7 on its respective half shaft 3 and 3a. Allowance must be made, of course, for a suitable amount of friction in the design of the barrel clutch.

The spools of the recording apparatus are arrested with the help of the brake magnets 29, 30, only the idling spool, which is being entrained merely by the record carrier, being arrested by the respective brake magnet under the control of switch 31. The braking efi'ort can be accurately adjusted by carefully setting the potentiometers 29b and 3012.

By providing additional switching elements, the barrel clutch according to the present invention can be readily remotely controlled by wire or radio.

1 claim:

1. A clutch-brake for electromagnetically reversing and braking the driving mechanism of a sound recording apparatus employing a wire or tape as the sound carrier comprising a shaft, a clutch disc for driving said sound carrier mounted directly and freely rotatable on said shaft, a sleeve on said shaft, a cup-formed magnet slidable on said sleeve for a limited axial movement for driving said clutch disc when energized, means for rotating said magnet and a brake magnet cooperating with said clutch disc.

2. A clutch-brake for precision apparatus particularly sound recording apparatus comprising a shaft, a clutch disc mounted freely rotatable on said shaft, a sleeve on said shaft, a cup-formed magnet on said sleeve for driving said clutch disc when energized, means for rotating said magnet, an elastic element interposed between said magnet and said means for rotating said magnet, and a brake magnet cooperating with said clutch disc.

3, A clutch-brake for precision apparatuses particularly sound recording apparatuses comprising a pair of aligned shafts, a paramagnetic element located between said shafts, a sleeve mounted on said shafts, a freely rotatable clutch disc mounted upon each shaft, a pair of ferromagnetic hollow cores mounted upon said sleeve, a non-magnetic element fixedly connecting said hollow cores, an electromagnet encircling each core, a pulley mounted upon said connecting element, a spiral spring connecting .said pulley with said interconnecting element so as to rotate said magnets on said sleeve and a brake magnet cooperating with each of said clutch discs.

4. A clutch-brake for precision apparatuses particularly sound recording apparatuses comprising a pair of aligned shafts, a paramagnetic element located between said shafts, a sleeve mounted on said shafts, a freely rotatable clutch disc mounted upon each shaft, a pair of ferromagnetic hollow cores mounted upon said sleeve, a non-magnetic element fixedly connecting said hollow cores, an electromagnet encircling each core, a pulley mounted upon said connecting element, a spring connecting said pulley with said interconnecting element so as to rotate said magnets on said sleeve, and a fixed regulatable extraneously energized electrical brake means having its pole-pieces partially embracing said clutch discs with an air gap in between.

References Cited in the file of this patent UNITED STATES PATENTS 2,324,693 Griswold et a1 July 20, 1943 2,594,775 Herst et a1. Apr. 29, 1952 2,595,190 Edwards Apr. 29, 1952 2,612,248 Feiertag Sept. 30-, 1952 2,642,169 Hutchison June 16, 1953 2,800,210 Muller July 23, 1957 2,801,720 Bachman Aug. 6, 1957 2,851,138 Straub et al. Sept. 9, 1958 2,872,003 Nussbaumer Mar. 3, 1959 

